1. Field of the Invention
The present invention relates to a mechanism which locks the actuator arm of a hard disk drive assembly.
2. Description of Related Art
Hard disk drives typically have an actuator arm which can move relative to a magnetic disk that is rotated by an electric motor. At the end of the actuator arm is a magnetic head which can magnetize or sense the magnetic field of the disk. The magnetic head is typically separated from the surface of the disk by an air gap that is on the order of 0.06 microns in length. Any contact between the head and the magnetic disk may result in a loss of data or possible damage to the disk.
Hard disk drive units that are used in portable computers are more likely to be subjected to external shock or vibrational loads. For example, the user may drop the computer, or the computer may be transported within a vehicle that applies a vibrational load to the disk drive unit. The application of an external force to the drive unit may cause the magnetic head to strike or otherwise come into contact with the disk when the disk is not spinning. It is therefore desirable to have a hard disk drive which reduces the likelihood of damage to the magnetic disk when the drive unit is subjected to an external load.
Some magnetic disk contain a landing zone where the magnetic head is positioned when no power is supplied to the drive unit and the disk is not spinning. The landing zone is a blank area of the disk where data is not normally stored. Thus any shock or vibrationally induced contact between the head and magnetic disk surface will not damage the disk.
When the disk is spinning, the actuator arm and head are located adjacent to a read/write zone of the magnetic disk. When power to the drive unit is terminated, such as when the computer is turned off, the control logic of the hard disk drive rotates the magnetic head above the landing zone. The motor is sometimes used as a generator that supplies power to the actuator arm during the power down cycle of the drive unit.
As the motor reduces speed, less power is supplied to the coils of the actuator arm. Consequently, the magnetic head can skew off of the landing zone of the disk. Additionally, the actuator arm may rotate away from the landing zone if the disk drive is subjected to an external load. It would therefore be desirable to have a hard disk drive which locks the magnetic head above the landing zone when power to the drive unit is terminated.